1. Field of the Invention
The present invention relates to the field of local area networks (LANs) using the Ethernet communication protocol (e.g., the IEEE 802.3 Standard). Specifically, the present invention relates to an arbitration mechanism and process for multiple circuits having auto-negotiation sessions.
2. Related Art
Communication networks for computer systems are an extremely popular form of providing network computing today. FIG. 1A illustrates a high level block diagram of the communication levels within a typical communication network system 5System 5 has a first communication level 6 including communication adapters ("cards") that are inserted into computer systems to provide them with networking capability. The computer systems interface with users 4. The second communication level 7 is the workgroup level and includes hubs (e.g., repeater hubs, switching hubs, etc.). The hubs provide communication pathways between computer systems of the same or multiple local area networks (LANs). Computer systems coupled to a common hub share the same collision domain. A collision domain is a group of computer systems logically connected to share the same physical bandwidth (e.g. 10 Megabits/sec or 100 Megabitstsec) of a communication pathway. In the field of twisted pair cable repeater hubs, a collision domain is managed by a repeater interface controller (RIC). The third level 8 is often called the backbone or backplane level and can include segment switches. Among other functions, the components of level 8 provide communication pathways between hubs and between different collision domains.
FIG. 1B illustrates an exemplary prior art communication configuration including a hub 10 (or switch) and a computer system 30. The computer system typically contains one adapter card 35 which contains physical layer communication circuitry for establishing and maintaining communication over a communication line 20 (e.g., twisted pair wires). In the configuration 12 of FIG. 1B, the other end of the communication line 20 is coupled to port circuitry 15 of the unmanaged hub 10. The port circuitry 15 also contains physical layer communication circuitry for establishing and maintaining communication over communication line 20. The port circuitry 15 and the adapter card 35 can each contain physical layer circuitry that support multiple communication rate capabilities. For instance, port circuitry 15 and the adapter card 35 each can contain circuitry for communicating at 10 Base T (10 Megabits per second) capability and also 100 Base TX (100 Megabits per second) capability. Also, half or full duplex communication is typically supported. Alternatively, port circuitry 15 and the adapter card 35 each can contain circuitry for communicating at 10 Base T capability and also 100 Base T2 capability; again, half or full duplex is also supported.
With respect to the examples above, an auto-negotiation session is performed in accordance with the well known IEEE 802.3 standard in which the port circuitry 15 and the adapter card 35 engage in communication negotiation ("negotiation") to select between 10 Base T and 100 Base TX (half or full duplex) in one example, or between 10 Base T and 100 Base T2 (half or full duplex) in another example. The auto-negotiation session is generally performed such that the best obtainable communication speed is selected that can be supported by both ends of the communication line 20. As is well known within the IEEE 802.3 auto-negotiation processes, the physical layer communication circuits located on either end of the communication line 20 broadcast special data packets ("link packets") specifically designed to contain an identification of the communication capabilities of the data packet originator.
Auto-negotiation problems arise, however, when two or more physical layer capabilities are combined in a single circuit device, e.g., either combined in the adapter card 35 and/or combined in the port circuitry 15. For instance, problems arise when 100 Base TX physical layer circuits and also 100 Base T2 physical layer circuits are combined in the adapter card 35 and/or combined in the port circuitry 15 This type of physical layer combination is implemented ostensibly to provide robust physical layer capabilities for the devices in a network system. In these cases having combined physical layer capability, separate auto-negotiation circuits are implemented in each device. Problem occur because each physical layer circuit attempts to perform auto-negotiation (e.g., as between 10M and 100M communication and as between full and half duplex) on its own, e.g., autonomously, irrespective of the other circuit to which it is combined. When two or more physical layer communication circuits (that are combined) attempt to perform auto-negotiation simultaneously on the same communication line 20, the auto-negotiation sessions fail for both devices thereby impeding communication over line 20.
For instance, in an adapter having both 100 Base TX and 100 Base T2 physical layers in combination over a single communication line 20a first auto-negotiation session performed over line 20 as between 100 Base TX and 10 Base T will interfere with a second auto-negotiation session performed over line 20 as between 100 Base T2 and 10 Base T; the 100 Base TX and the 100 Base T2 physical layer circuits each having a respective 10 Base T capability and supporting full and half duplex. In effect, the IEEE 802.3 standard state machines were not designed to take into account the possibility of having multiple physical layer communication circuit capabilities combined on the same communication device and sharing the same end of a communication line 20.
Accordingly, what is needed is a circuit and method for allowing auto-negotiation processes to occur within devices that have combined physical layer capabilities that also share a same end of a communication line. What is needed further is a circuit and method for allowing auto-negotiation processes to occur within devices that have combined 100 Base T2 and 100 Base TX physical layer capabilities and that also share a same end of a communication line. What is needed yet further is a circuit and method for allowing auto-negotiation processes to occur within devices that have a 1000 Base T physical layer circuit combined with either 100 Base T2 physical layer capability or 100 Base TX physical layer capability and that also share a same end of a communication line. The present invention provides such advantageous functionality. These and other advantages of the present invention not specifically mentioned above will become clear within discussions of the present invention presented herein.